diff --git a/src/cq/src/cqMain.c b/src/cq/src/cqMain.c
index 13f3c0a2b0a0a75e07329a24f13ab0b9a274d3ac..769dfea774b86c9cd420edcd1b15d1020da3a67f 100644
--- a/src/cq/src/cqMain.c
+++ b/src/cq/src/cqMain.c
@@ -256,11 +256,30 @@ static void cqProcessStreamRes(void *param, TAOS_RES *tres, TAOS_ROW row) {
   SDataRow trow = (SDataRow)pBlk->data;
   tdInitDataRow(trow, pSchema);
 
+  union {
+    char buf[sizeof(int64_t)];
+    tstr str;
+  } nullVal;
+
   for (int32_t i = 0; i < pSchema->numOfCols; i++) {
     STColumn *c = pSchema->columns + i;
     char* val = (char*)row[i];
     if (IS_VAR_DATA_TYPE(c->type)) {
-      val -= sizeof(VarDataLenT);
+      if (val == NULL) {
+        val = nullVal.buf;
+        if (c->type == TSDB_DATA_TYPE_BINARY) {
+          setNull(nullVal.str.data, TSDB_DATA_TYPE_BINARY, 1);
+          nullVal.str.len = 1;
+        } else {
+          setNull(nullVal.str.data, TSDB_DATA_TYPE_NCHAR, 4);
+          nullVal.str.len = 4;
+        }
+      } else {
+        val -= sizeof(VarDataLenT);
+      }
+    } else if (val == NULL) {
+      val = nullVal.buf;
+      setNull(val, c->type, c->bytes);
     }
     tdAppendColVal(trow, val, c->type, c->bytes, c->offset);
   }
diff --git a/src/inc/taos.h b/src/inc/taos.h
index bf6942be8b7ddff9ffff4af222fb5e938e63d096..9ac97a24e1d4bb695b4f1a30516b9799b6ad89eb 100644
--- a/src/inc/taos.h
+++ b/src/inc/taos.h
@@ -55,7 +55,7 @@ typedef enum {
 typedef struct taosField {
   char     name[65];
   uint8_t  type;
-  short    bytes;
+  uint16_t bytes;
 } TAOS_FIELD;
 
 #ifdef _TD_GO_DLL_
diff --git a/tests/script/general/parser/alter.sim b/tests/script/general/parser/alter.sim
index 44c12fa968d52b7c6e3811d4997e549af3bba7bf..c30cc171bc519ef17928d2db722025149788a2f3 100644
--- a/tests/script/general/parser/alter.sim
+++ b/tests/script/general/parser/alter.sim
@@ -137,7 +137,7 @@ sleep 6000
 sql insert into tb1 values (now, 2, 'taos')
 sleep 3000
 sql select * from strm
-if $rows != 1 then
+if $rows != 2 then
    return -1
 endi
 if $data04 != 1 then
@@ -148,7 +148,7 @@ sleep 6000
 sql insert into tb1 values (now, 3, 'taos', 3);
 sleep 3000
 sql select * from strm
-if $rows != 1 then
+if $rows != 3 then
    return -1
 endi
 if $data04 != 1 then
@@ -188,9 +188,9 @@ sql create table tb using mt tags(1)
 sleep 3000
 sql insert into tb values ('2018-11-01 16:30:00.000', 1, 'insert', 1)
 sql alter table mt drop column c3
-# the below query should be deleted after bug fix
+
 sql insert into tb values ('2018-11-01 16:29:59.000', 1, 'insert')
-sql_error import into tb values ('2018-11-01 16:29:59.000', 1, 'import')
+sql import into tb values ('2018-11-01 16:29:59.000', 1, 'import')
 sql select * from tb order by ts desc
 if $data01 != 1 then
   return -1
@@ -203,13 +203,13 @@ sql select * from tb order by ts desc
 if $data03 != NULL then
   return -1
 endi
-# the query below should be deleted after bug fix
+
 sql reset query cache
 sql insert into tb values ('2018-11-01 16:29:58.000', 2, 'import', 3)
-sql_error import into tb values ('2018-11-01 16:29:58.000', 2, 'import', 3)
+sql import into tb values ('2018-11-01 16:29:58.000', 2, 'import', 3)
 sql import into tb values ('2018-11-01 16:39:58.000', 2, 'import', 3)
 sql select * from tb order by ts desc 
-if $rows != 2 then
+if $rows != 4 then
   return -1
 endi
 if $data03 != 3 then